People's interest in crime prevention is increasing every year, and particularly, in recent years home security for protecting home from burglaries or the like is attracting high attention. As one way to achieve home security, services are provided by security companies, in which, typically, a security sensor installed in a user's house responds to entry of a burglar or the like to notify it to the security company with which the user has contracted, such that security guards are sent to the house to deal with the incident.
Aside from such relatively large-scale services provided by security companies, technology is known in which, in an intercom system including an intercom handset located near the boundary of the premises of a building and an intercom base unit located inside the building, a human body detection unit is connected to the intercom base unit to detect a human body at or near a doorway of the building and determine whether there is an abnormality (see JP2008-059311A).
Also known is technology in which a handset of a cordless telephone system is provided with an intrusion detection unit for detecting intrusion of a suspicious person or the like and a transmission unit for transmitting intrusion information acquired by the intrusion detection unit to a base unit, and the base unit is provided with a security action performing unit that, upon receipt of the intrusion information from the transmission unit, assesses the content of the information and performs a prescribed security action (see JPH07-079291A).
However, in the home security systems configured to provide home security services of security companies, typically, sensors are mounted to or near windows and doors of each house to be monitored and a management device for collecting the outputs from the sensors is installed in each house, and further, lines are necessary to connect each management device with a central device operated by the security company. Thus, the cost of laying the lines and installing the management device in each house tends to increase the total cost of the system.
The technology disclosed in JP2008-059311A can realize a security system with a relatively small-scale structure. However, the system uses, as a human body detection unit, a passive infrared sensor (which may include a pyroelectric sensor, an ultrasonic sensor, an optical sensor, a thermopile or the like), and addition of such a sensor and a circuit for processing the output from the sensor inevitably increases the cost of the system.
The technology disclosed in JPH07-079291A also can realize a system with a relatively small-scale structure. However, as is the case with the system disclosed in JP2008-059311A, the system of JPH07-079291A also uses an infrared sensor as a human body detection unit (intrusion detection unit), which leads to an increase in the cost.